Method and apparatus for excavating with an endless bucket line

ABSTRACT

For underwater excavating I employ a hull having a well. The hull supports a pair of catenary terminals relatively movable toward and away from each other. The terminals may be in the form of rotary drums. Both drums are mounted on the hull for yielding movement such as pivoting about a fore and aft horizontal axis. A continuous flexible line is supported from the hull by being trained around the drums and extends in a catenary curve below the hull to a variable depth controlled by varying the length of the line along the catenary. The line is advanced in a predetermined direction by a driver operating one or more of the drums. Supplemental suspension lines fasten excavating buckets to the continuous line for limited movement. The buckets discharge into material handling equipment on the hull. Preferably, the line shape or catenary curve below the hull is variable by another catenary terminal in the form of another rotary drum, idle or driven, suspended from the hull and movable fore and aft thereon, usually in company with one of the hull mounted drums. The other or additional rotary drum also can swing laterally and fore and aft and can be raised and lowered; i.e., projected and retracted, affording universal yielding movement. If desired the line can be doubled to include two lines in spaced parallel planes and of similar curvature, the buckets being flexibly fastened to both lines, if desired. Also, the line or lines can carry floats.

United States Patent 1 [111 3,766,671

Guntert 1 Oct. 23, 1973 METHOD AND APPARATUS FOR EXCAVATING WITH ANENDLESS BUCKET [57] ABSTRACT LINE For underwater excavating I employ ahull having a [76] Inventor g g g p ggif well. The hull supports a pairof catenary terminals 00 relatively movable toward and away from eachother. [22] Filed: Dec. 20, 1971 The terminals may be in the form ofrotary drums. Both drums are mounted on the hull for yielding [21] Appl'209584 movement such as pivoting about a fore and aft horizontal axis. Acontinuous flexible line is supported [52] U.S. Cl 37/69, 37/195,198/116 fr m he hull by being tr ined around the drums and [51] Int. Cl.E02f 3/14 xtends in a catenary curve below the hull to a vari- [58]Field of Search 37/69, 60, 72; able depth controlled by varying thelength of the line 198/116, 12; 214/15; 114/,5 along the catenary. Theline is advanced in a predetermined direction by a driver operating oneor more of [56] Referen es Cited the drums. Supplemental suspensionlines fasten exca- UNlTEDSTATES PATENTS vating buckets to the continuousline for limited movement. The buckets discharge into material han-'33332 ,mfi sf 223 dling equipment on the hull. Preferably, the lineshape 3 146'537 9/1964 Von 37/69 or catenary curve below the hull isvariable by another 3,672,079 6/1972 Masuda at a] my/69 catenaryterminal in the form of another rotary drum, 3,437,064 4/1969 i-iiT g k114/5 13 idle or driven, suspended from the hull and movable 2,636,2884/1953 Thomas 37/69 X fore and aft thereon, usually in company with oneof 530,675 12/1894 Ball 37/69 the hull mounted drums. The other oradditional ro- FOREIGN PATENTS 0R APPLICATIONS tary drum also can swinglaterally and fore and aft and can be raised and lowered; i.e.,projected and re- 1 giigr g tracted, affording universal yieldingmovement. If de- 14:435 7/1891 Great 37,69 sired the line can be doubledto include two lines in 1,148,751 4/1969 Great Britain 37/72 SpacedParallel Planes and of Similar curvature, the

Primary Examiner-Robert E. Pulfrey Assistant Examiner-Clifford D.Crowder Attorney-Mark Mohler et al.

buckets being flexibly fastened to both lines, if desired. Also, theline or lines can carry floats.

22 Claims, 20 Drawing Figures PATENTEDumzsm: 3.766571 SNEEI 020F 10 IN VEN TQR.

RONALD M. GUNTERT BY v nj w gut {la/(1A ATTORNEYS 3.7es;e71

SHEU OBUF'IO PATENTEU IN 23 I875 RONALD M BY W4 flfd aw JM ATTORNEYSPAIENlEnlclzalm 3.766571 SHEET 0501- 10 INVENTOR. RONALD M GU/VTER W777% Maw AT TOR A/EYS PATENIEuumzms 3.766571 SHEET 07 0F 10 FIG. 8.

INVENTOR.

RONALD M 6U/V7EA7' ATTOFWVEYS PATENT-ED116123 ms SHEET 08 0F 10INVENTOR. RONA L0 /V/. GUNTfAT BY fi Ma 49 M AT TORNEVS METHOD ANDAPPARATUS FOREXCAVATING WITH AN ENDLESS BUCKET LINE T recover materialsituated beneath any kind of a water body, particularly material atseveral hundred feet below the surface, and to do so satisfactorily,without equipment damage and economically over a long period, isdifficult or often impossible without special facilities and methods.Although there are many and varied recovery problems in variousenvironments, particular attention at present is being given to theproblem of excavating bottom material beneath the ocean either for itsown sake or for values it contains, or both. For use in thatcircumstance and also in other environments, I havev conceived of anexcavating machine and manner of excavating having certain fundamentalcharacteristics that can be varied to suit a wide range of operatingconditions.

While only two of the numerous different possible forms or particularembodiments of the fundamental invention are disclosed in detailhereinafter, my underwater excavator concept can be considered generallyas including a support; for example, an elongated hull designed forsufficient buoyancy on a water body, such as but not necessarily theocean.

Suspended from the hull by suitable suspending means is a flexible,endless or looped line. Under the influence of gravity such a line, whensupported at two separate points, hangs in a vertical plane and partakesof the shape of a catenary curve. This is true of the line between oraway from points of support. At such sup port points or contact surfacesthe line, in practice, touches the point or conforms to the surface, inthe latter instance usually departing from a catenary curvature. Suchpoint or contact with a differently curved support surface and in factany point or surface that causes the line to depart from a catenarycurve I call a terminal point or line guide" whether it is a stationaryor movable mathematical point or the effective portion of a linecontacting surface.

In a practical instance, on the water support or hull I provide a pairof terminal points in the form of rotary line guiding or engagingmembers such as sheaves, wheels, drums or the like. These are mounted onthe hull for rotation about turning axes normal to the plane of the lineand are themselves largely situated in such plane. At least one of theserotary members is propelled or rotated by suitable machinery and isreferred to as a driving drum since it advances the line in apredetermined direction, usually a horizontal direction parallel to thelength of the hull and conveniently along the center line thereof. Theother rotary member may also be driven but usually is not driven so isreferred to as a dry or hull idler drum.

I vary the shape of the catenary curve of the line by moving the drumsrelative to each other, usually by relative movement in thepredetermined direction. While both drums can be moved relative to thehull, it is, in practice, usually desirable to move only one drumrelative to the hull. For example, the driving drum is movablelongitudinally of the hull. Since the range or amount of the movement ofthe drums relative to each other is extensive, I provide alongitudinally extending central well in the hull through which the linedepends and above and over which at least one of the drums islongitudinally movable.

Trained over the driving drum for advancement by it and also trainedover the hull idler drum is the line or digging line. This is offlexible material, such as a chain,

having an upper run preferably in part hanging free and extending in theair between the two drums. The remainder of the line constitutes a lowerrun largely disposed in the water and depending from the two drumsacting as catenary curve terminal points at about the same elevation.Diggers such as'dragline buckets are connected to the digging line. Thelength of the line is such that the bottom of the catenary curve is inor near the desired digging zone. When the hull idler drum and thedriving drum are moved relatively closer together, the bottom of theline having the catenary curve shape is lowered, and when the hull idlerdrum and the driving drum are moved relatively farther apart, the bottomof the line having the catenary curve shape is raised. This is one wayof adjusting the digging depth. For a given length of line and hulllocation, if the hull drums are far enough apart and the digging depthis relatively shallow, it is possible to pay out sufficient line so thatthe line'curvature is altered. For example, a substantially vertical runof line may extend from the hull driving drum to a subjacent point onthe bottom. The line from that bottom point to the surface may describea new catenary curve between the point at the bottom and the terminalpoint on the hull. The line configuration may be modified by extensivebottom contact.

For great depths, catenary curves originating at terminal points ofsubstantially equal elevation require a long line and a long hull. Forthis and other reasons, I prefer to provide means affording anadditional means in the form of another terminal point or line guidingunit for the catenary curvature of the line and to dispose this terminalpoint below the hull in the water near the bottom or excavating zone andusually in the same longitudinal, vertical plane defined by the freelyhanging line. This additional or third terminal point is, in practice,established by a wheel, sheave, drum or the like engaging the line andwhich may be driven but usually is a free running idler. This Isometimes refer to as a fairlead. As a support for the additionalterminal point or wet idler, I provide means supporting the idler forrotation about an axis normal'to the mentioned vertical plane and inselected locations relative to the hull. This supporting means can takevarious different constructional forms, and in the present instanceincludes a frame or beam-like member referred to as a boom. While it canbe stationary, the boom is mounted with respect to the hull to swingabout a horizontal, transverse rotary axis usually substantiallycoincident with and preferably also travelling fore and aft with theaxis of one of the hull drums, preferably the driving drum. The boomposition is variable from a position that is approximately vertical to aposition that is approximately horizontal. Swinging movement about therotary axis is controlled by a tackle effective in tension to hold theboom is a selected, angular or polar position and effective laterally tohold the boom against excess transverse shifting. The boom is preferablyU-shaped to straddle and swing below the hull. It is conveniently madehollow and buoyant. By varying ballast in the boom, the depth of theboom below the hull can be changed to selected levels without the use ofthe tackle. The boom can thus partake of retraction and extensionrelative to the hull. i

The lower end of the boom extends horizontally between the boom legs andcarries the additional, wet or boom idler drum in a position engagingthe line. When the boom is approximately vertical, the line between theterminal points established by the hull driving drum and the boom idlerdrum is also approximately vertical. The catenary curve from the boomidler drum to an idler drum on the hull is about half the length of acorresponding catenary curve from two points at the elevation of thedriving drum to the same depth as the boom idler drum.

Perhaps more important, the catenary curve of the line as shaped by theboom idler drum has an appreciable portion near the boom idler drum thatis approximately horizontal for a substantial distance, so that there isa relatively long path of engagement of the diggers with the(approximately horizontal) bottom.

In cases wherein the water may be rough, and in any case to allow forside to side rocking of the hull while permitting the boom, the drumsand other line engaging machinery to be relatively stable close to avertical plane, I mount the driving drum and the hull idler drum foruniversal yielding movement relative to the hull in a transversedirection. This can be done in various ways and allowing various amountof freedom, but preferably I provide for motion about a common, fore andaft, central axis, so that reasonable rocking of the hull can occurwithout corresponding rocking of the boom or line. The amount of freedomis set by the design and is intended to take care of the allowablecircumstances.

The diggers on the line are preferably in the form of dragline bucketssecured to the line directly or, as is usually preferred, by flexible;i.e., non-rigid, connecting lines or chains of especially chosen lengthsso that the buckets have some limited freedom of movement with respectto the digging line. There is no rigid connection between the diggingstructure near the water bottom and the hull, a factor of importance inreducing the chances of damage. The weight of the line and of thebuckets attached thereto can be materially offset by floats attached toand moving with the line and serving as local supports.

In another version of the device, there is a double line; i.e., thereare two separate loops of digging line of the same out line or contourand disposed in vertical, fore and aft planes parallel to each other.The two lines are similarly trained over the several drums. The doubleline or two lines are held in transverse relationship to each other bycross spacers extending between them. Both lines engage the same drivingdrum or coupled driving drums so that the lines are held in phase orsquare" with each other. In the duplex version also, floats may beattached to the double line or two lines. When spacers are used, thespacers themselves maybe buoyant to serve as floats.

Material removed from the bottom by the buckets is appropriately handledby equipment on the hull. This may include devices for discardingunwanted sizes, for separating values, for recovering values mixed inthe excavated material, and the like.

While the invention illustrated is for underwater excavation, andcertain features are particularly adapted for such use, it is apparentthat whether the succession of buckets are suspended from supports on ahull floating on a body of water or on other structure spaced above thebed of material to be excavated, most of the advantages of the controlsystem would be enjoyed. One example would be the removal of bulkmaterial from the hold of a ship or barge, or elsewhere.

In view of the foregoing summary and to meet the numerouscharacteristics of different excavating operation, it is an object ofthe invention to provide improvements in underwater excavating tooperate effectively without damage, economically and well, in instanceswhere such operation, prior to my invention, has not been possible,feasible or economical.

It is another object of the invention to provide an underwaterexcavating machine without rigid contact with the bottom by hullappendages or digging mechanism.

It is another object of the invention to provide an underwaterexcavating machine supported on the water and in which reasonablemovement of the supporting structure in the water does not disturb theexcavating operation.

Another object of the invention is to provide an underwater excavatingmachine effective, even at considerable depths, economically to removethe bottom material underlying the water body and transport suchmaterial to the water surface.

Another object of the invention is to provide an underwater excavatingmachine in which the operating power is relatively low.

A further object of the invention is to provide an underwater excavatingmachine which can be easily put into transport condition and so movedabout from place to place for advantageous excavation.

A still further object of the invention is to provide an underwaterexcavating machine in which the excavating units are carefully andaccurately handled and guided.

A further object of the invention is to provide an underwater excavatingmachine in which the recovery mechanism is closely associated with theexcavating machinery.

A further object of the invention is in general to provide an improvedunderwater excavating machine, particularly one for great depths.

An added object is the provision of an excavating machine for excavatingand removing material from a bed thereof in which an endless successionof flexibly connected digging buckets is suspended in the form of anendless loop which is controlled for excavating at different depths andin digging engagement for different periods of time free from injury tothe buckets.

Another object of the invention is the provision of an improved methodof excavating material from a bed thereof.

Other objects together with the foregoing are attained in theembodiments of the invention described in the accompanying descriptionand illustrated in the accompanying drawings, in which:

DESCRIPTION OF DRAWINGS FIG. A is a diagrammatic view illustrating infull and broken lines a conventional endless bucket line and its mannerof operation.

FIG. B is a diagrammatic view illustrating in full and broken lines onefeature of the operation of the present invention, and manner ofoperation.

FIG. C is a diagrammatic view illustrating in full and broken linesdifferent features of the present invention and method.

FIG. D is a diagrammatic view similar to FIG. C showing a feature of thepresent invention.

FIG. 1 is a side elevation, with some portions being showndiagrammatically and other portions being broken away, of an underwaterexcavating machine as it appears in its operating relationship.

FIG. 2 is a plan of the structure shown in FIG. 1.

FIG. 3 is a bow elevation of the structure shown in FIG. 1.

FIG. 4 is a stern elevation of the structure shown in FIG. 1.

FIG. 5 is a cross-section of the upper portion of the structure shown inFIG. 1, the plane of section being indicated by the line 5-5 of FIG. 1,certain parts being omitted for clarity.

FIG. 6 is a cross-section like FIG. 5 but with the plane of sectionindicated by the line 66 of FIG. 1, there being similar omissions.

FIG. 7 is a side elevation of a modified form of structure comparable tothat shown in FIG. 1, certain portions being broken away and otherportions being illustrated diagramatically.

FIG. 8 is a plan of the structure shown in FIG. 7.

FIG. 9 is a bow elevation of the structure shown in FIG. 7.

FIG. 10 is a stern elevation of the structure shown in FIG. 7.

FIG. 1 1 is a cross-section of the upper portion of part of thestructure shown in FIG. 7, the plane of section being indicated by theline 11-11 of FIG. 7, certain parts being omitted for clarity.

FIG. 12 is a cross-section somewhat like FIG. 11 but with the plane ofsection being indicated by the line 12-12 of FIG. 7, there being similaromissions.

FIG. 13 is an elevation of a buoyant spacer shown to an enlarged scale.I

FIG. 14 is an end elevationof the structure shown in FIG. 13.

FIG. 15 is a side elevation to a greatly enlarged scale of a dragbucket.

FIG. 16 is an end elevation of the drag bucket shown in FIG. 15,

GENERAL DESCRIPTION Introductory to the particular'description, in FIG.A the bucket line 2with which the buckets are flexibly connected, is anendless loop trained around a pair of supports 1, 21 fixedly spacedapart above the bed 7 of material to be excavated, the supports beingshownas carried on a hull 11 that, in turn, overlies the bed. To be ofpractical use, the bucket line 2 has had sufficient slack to form afalse catenary terminal at 4 on the bed 7, positioned approximatelybelow one of the supports.

With this arrangement the control of the digging depth is not possibleand the maximum digging depth is indicated by the broken line positionof line 2, which is in the form of a true catenary.

FIG. B shows the support 21, which will becalled the driving drum, assupported for movement toward the support 1, or idler drum, which is oneof the features of the present invention. In this instance, although theline 2, depending from the supports 1, 21 were a true catenary making apoint contact with the bottom, the digging depth indicated by the linein the broken line position would be substantial and the digging depthcan be controlled.

In the arrangement of FIG. A and B, the ability to clean a bottom is notpossible. By cleaning the bottom is meant the horizontal movement of thebuckets along a horizontal level at the desired depth below the top ofthe bed. I

Were a line of greater length provided than is shown in FIG. B, therewould be no control of the resistance encountered by the buckets.

In FIG. C a substantially vertical boom 36 is movable along the hullwith the driving drum and carries a boom idler drum 55 over which line 2is trained at the lower end of the descending line from drum 21 with thelower portion 6 forming a flattened catenary adapted to clean up abottom at any digging level and this digging depth is controlled by theposition of drum 21 combined with the position of boom 36.

Boom 36 may be pivoted through the different broken line positions 8 forcarrying the depending portion of the loop or bucket line 2 to differentheights.

While the diagrams show some of the principal line positions possible,it should be understood that excavating or drag line buckets 64 as shownin FIG. D, are nonrigidly or flexibly connected to the line, or lines,so that while they generally follow the line contour, they aresufficiently free, within limits, to dig at somewhat deeper depths andto move with partial independence, so that the bottom conditions are notadversely or excessively reflected to the line or to the boom or hull.

PARTICULAR DESCRIPTION Underwater excavation pursuant to my inventioncan be accomplished on virtually any body of water and is hereindisclosed as it is performed by machines in two principal commercialforms. In both forms the machine floats on a water body 6 disposed abovea bottom 7 on which material 8 to be excavated is found. As an exampleonly, the distance between the level of the water 6 and the bottom 7 isshown as approximately feet, with 50 feet of material available fordigging. However, the machine is capable of taking materials from anelevation just below the bottom of the hull down to the bottom 7, adistance that can be 'of the order of 600 feet.

Adapted to float in water 6 is a boat or hull ll of a buoyant nature andof generally standard construction. The hull is positioned or anchoredat selected locations by appropriate lines (not shown) in the customaryway. The hull has, as particularly shown in FIG. 2, a reentrant well 12in its bow 13 and has cut away sides 14 and 16 in the after portion.Likewise there is a reentrant well 17 extending into the hull from thestern 18.

Adapted to be supported on the deck 19 of the hull is a catenaryterminal in the form of a driving drum 21 of appropriate constructiondesigned to rotate on an axle 22 about a transverse axis and supportedon a suitable framework 23. A motor or engine driving device 24 isconnected to rotate the driving drum normally in a clockwise direction,as seen in FIG. 1. Since it is desired to move the framework 23 fore andaft into various locations along the center line of the hull deck 19 andover the well 17, the framework is supported on anti-friction devicessuch as sliding feet 26 operable in a longitudinal, central directionalong guides 27 and 28 arranged symmetrically and extending in a foreand aft direction on the deck.

In order to move and hold the framework 23, suitable means are provided.As an example, a pair of hydraulic cylinders 29 and 31 are mounted onthe deck with their plungers 32 and 33 connected to the framework tomove it between a forward position, as shown by the solid lines in FIG.2, and an after position, as shown by the dotted lines in FIG. 2, and tohold the framework in those positions or in any intermediate position.The hydraulic mechanism, by the usual piping and valving, secures theframework 23 in any selected fore and aft position despite substantialloads imposed upon it.

Designed to cooperate with the hull is a duplex boom generallydesignated 36. As particularly shown in FIGS. 3 and 4, the boom includesa pair of legs 37 and 38 at their bottom joined by a cross beam 39. Theboom is preferably of hollow construction and by itself is buoyant inthe water. The boom is designed to rise and fall; i.e., retract andextend, and to swing. The legs move alongside the cut away sides 14 and16 of the hull. The boom is held or restrained in any of its particularfore and aft or angular positions by appropriate collars 41 and 42slidable on the upper portions of the legs 37 and 38. The collars areconnected by cables 43 and 44 to the framework 23. Thus, as theframework 23 travels forward and aft, the collars 41 and 42 aresimilarly moved and correspondingly move the boom fore and aft spanningand alongside the hull. At the same time, the boom is also angularlylocated or rotated and restrained by a pair of laterally spread, tensionstern lines 46. At one end these are secured to laterally spaced pointsat the lower portion of the boom 36. At the other, upper end, the lines46 travel around a pair of close sheaves 47 on a superstructure 50 andthen connect to an appropriate winch mechanism, not shown.

The result of this mooring of the boom is that the boom can be swungbetween a substantially vertically upright, working position, as shownby the full lines in FIG. 1, and an approximately horizontal, cruisingposition, as shown bythe dotted lines in that figure. The boom swingingaxis is exactly or approximately coincident with the transverse cables43 and 44 and the axle 22. The boom and its swing axis can be bodilymoved fore and aft along the hull by correspondingly moving theframework 23. The boom can also rise and fall in a vertical directionrelative to the hull. In fact, by combining the various swinging,horizontal and vertical boom motions the operator can move the boom intoand can hold it in a wide variety of positions with respect to avertical plane extending along the bow-stern center line of the hull.This provides various digging depths and positions as well as a shallowdraft position for transportation.

Since the boom is hollow and is buoyant, its depth is altered andcontrolled by pumping water into it or extracting water from it. Forthat reason, as particularly shown in FIG. 2, there is provided on thedeck 19 a pump 51 appropriately driven and controlled. The pump iseffective through a cross pipe 52 and flexible hoses 53 and 54 to putwater into the hollow legs 37 and 38 and into the bottom hollow beam 39of the boom. When the boom weight is thus made greater, the boom tendsto lower, the legs sliding through the collars and pulling down thestern tension lines 46 when they are free. When the pump is reversed,then water is taken out of the interior of the hollow boom and is wastedoverboard until the boom is sufficiently light to float up to thedesired elevation. The stern lines are correspondingly taken in. Byappropriate manipulation of the driving drum 21, of the hydrauliccylinders 29 and 31, and of the pump 51, as well as the stern lines 46,the boom can be maneuvered into a number of locations and positions andis well maintained in chosen positions by tension in the stern lines.

Mounted to rotate freely at the lower end of the boom 36 is a flangedboom idler drum 55 or wet idler drum designed to turn on a transverseaxle 56 about a transverse axis. In a comparable fashion, there isprovided a dry or hull idler drum 57 mounted to rotate on a transverseaxle 58 about a transverse axis. The axle 58 is disposed on asuperstructure 59 at the bow of the hull 11. The construction of thehull idler drum 57 is substantially the same as that of the boom idlerdrum 55.

Trained around and forming a loop about the driving drum 21, the boom orwet idler drum 55 and the hull or dry idler drum 57 is a line 61 of aflexible, strong material such as cable or chain. This is a single linewhich has central engagement with the driving and idler drums so thatthe line is advanced by the driving drum rotation. It is sometimesadvisable to have an auxiliary drum 62 similar to the idler drum 57 atthe bow of the hull simply to maintain an appropriate line contour.

The configuration of the line 61 between the driving drum 21 and the wetidler drum 55 is usually an approximately vertical straight line,although the line inclines with swinging of the boom 36. It is sometimesthe practice, primarily to stabilize against surge, to position the boom36 and the line 61 somewhat off vertical.

The carriage for the framework 23 and the boom travels fore and aft. Theupright or substantially upright or vertical position of the boom and ofthe line 61 thus can readily be maintained. The line is kept in tensionby raising and lowering the boom or, alternatively, by moving theframework 23 fore and aft or by moving the carriage of the framework 23as the boom depth is changed or by swinging the boom. Between the idlerdrum 55 and idler drum 62, if used, or the idler drum 57, theconfiguration of the line 61, where not otherwise supported, issubstantially that of a catenary curve.

Due to the elevation or level of the line supports,

- there is a nearly flat or horizontal portion of the line leaving theidler drum 55. If the line is permitted to run along the bottom, itapproximates the bottom contour, while the subsequent line portion, awayfrom the bottom, describes a new catenary curve. Between the idler drum57 and the driving drum 21 the shape of the line is a relatively flatcatenary curve except for the line portion that is supported. I preferalways to leave some unsupported line for spring effect to cushion shockloads or overloads.

Particularly pursuant to the invention, the line 61 at appropriateintervals thereon has securing means 63. These are generallyenlargements of the line 61 capable of passing over the various drumswithout difficulty. Connected to the line 61 and particularly to thesecuring means 63 thereon are diggers such as drag buckets 64. Each ofthe buckets is configured substantially as shown in FIGS. 15 and 16 andincludes a transversely and longitudinally tapered, rectangular bodyhaving a generally semi-circular end 66 approximately centered onconnecting lugs 67 and has a digging lip 68 thereon with bottom and sideteeth. Ears 69 at the forward end of the bucket have alternately usableapertures 71. The closed top of the bucket has a curved surface 72designed to fit the similar, circular cylindrical curved surfaces of thedrums 21 and 57.

the lugs 67 and other bridle chains engaging a selected 7 pair of theapertures 71. A forwardly extending head line 73 and a stabilizing,rearwardly extending tail line 74 unite with the respective, adjacentsecuring means 63.

Some or most of the vertical load is taken from the line 61 by floats 75fastened to the securing means 63. These floats are buoyant membersconnected to the line 61 and exert a generally upward force particularlyeffective in assisting in overcoming the weight of the line 61 and itsappurtenances.

The position of the buckets during their circuit is typically as shownin FIG. 1. As a bucket 64 approaches the driving drum 21, for example,it is partially oriented and lifted by a ramp 76 so that the bucketreadily rounds the drum and then is located by its own lines 73 and 74on the downgoing portion of the line 61. The bucket continues around theboom idler drum 55 and advances inan excavating attitude. As the bucketencounters the bottom, the bucket weight is largely removed fromthe line61, so that irregularities in the bottom can be followed and excavatedby the bucket without disturbing the line 61 to an appreciable ordisadvantageous extent. That is, the buckets as they are advanced by theline 61 are neverthelessrelatively free to move limited vertical andlateral distances'with respect to the line 61. Forces due to bottomirregularities thus are not detrimentally transmitted to the idler drum55 nor to the boom nor to the hull. Also, motion of the line 61 due tohull heaving is not directly transmitted toand does not disturb thebucket path of excavation.

I As the bucket travels along substantially horizontally, to the left inFIG. 1, its lip 68 engages with the material 8 and strips off a portionof such material. Whatever values are included with the removed materialare likewise loaded into the bucket. The load is brought upwardly out ofthe water around the auxiliary drum 62 (if used), andaround the idlerdrum 57. At this juncture the rounding bucketis dumped onto a grizzly77.

The dumping impact of the bucket is controlled by the residue may flowthrough sluice boxes to a waste pump or tailing sluices. The dragbuckets after they are dis charged onto the grizzly 77 continue toadvance in the upper run of the line 61 and again encounter the ramp 76to travel again in the same loop.

During operation, the water surface 6 may be rough. For that reason,particular means are provided for mounting some of the equipment so thatrocking of the hull, within limits, is not harmful. As particularlyshown in FIG. 5, the carriage frame 23 for the driving drum 21 ismounted on a cradle 86 having a horizontal, fore and aft or longitudinalpivot axle 87 connecting the framework 23 to the sliding foot frame 26.With this journalled on a fore and aft or longitudinal, horizontal axle89 in turn mounted on a base frame 91 connected to the hull, so that thehull can rock or tilt as shown by the full line and broken linepositions without disturbing the superstructure and mechanisms attachedto it.

'In another embodiment of the invention, as particularly shown in FIG. 7and thereafter, the general arrangement is as previously describedexcept that the various driving and idler drums carry, as shown in FIGS.8 to 10, a pair of lines 101 and 102. Since they engage the same drivingdrum, the two lines are synchronized. These are parallel to 'each otherso far as their looping characteristics are concerned and are evenlyspaced apart by a number of fixing means 103 rate of bucket inversionand changing slack' in the bucket chains. This is affected by the sizeof the drum which affords a longer or shorter drop of the bucket, due tochain slack,'as it passes over the drum-to vary the unloading impact ofthe bucket above the grizzly. The drum size is varied by lagging orpadding around the drum to change its radius and so change the allowablechain slack and correspondingly the dumping impact.

As the bucket is dumped, the finer material passes through the grizzly.The coarser'material, particularly as shown in FIG. 3, is diverted ontoa divider 78 leading to a conveyor 79 from which the coarse material cango overboard or into a tail sluice or barge on one beam and to analternately usable conveyor 81 leading overboard or into a sluice box orbarge on the other beam. Large material having or carrying no values isthus immediately discarded in either chosen direction. Material passingthrough the grizzly 77 travels into a tromme] 82 of the usual sort withappropriate washing facilities, if needed. Waste material is transferredlengthwise through the trommel for discard, whereas the remainingmaterial passes through the trommel openings into a pump and pipecircuit 83 leading to sluice boxes, rotary jigs 84 or similar valuerecovering mechanism. The

or spacers all of the same length. These spacers are formedapproximately as shown in FIG. 13 so as to be non-fouling and includeend fasteners 104 and 106 engaged with the lines 101 and 102. Thespacers have hollowinterm ediate portions 107 so that the spacers arehighly buoyant. The spacers are mounted between the lines 101 and 102 topass readilyaround the various driving and idler drums.

In this instance each of the dragline buckets 64 instead'of having aforward bridle to a headline and instead of having a rearward bridle toa stabilizing line rather has four separate lines, as shown in FIG. 8.Thereare two tension or drag bow-lines 108 and 109 v as well as twostabilizing or carrier stern lines 111 and axis and about its owntransverse axis only a limited amount and cannot be tripped, tangled orinverted. It

is thus always maintained with its cutting edge 68 in position to moveagainst the material to be excavated.

The operation of this form of the structure is substantially the same aspreviously described since the various devices, except primarily for thedouble lines, are unchanged. An advantage of having the buoyant spacers103 is that they support the weight of the line and the buckets to theextent desired, thus relieving strain and weight on the line and on thedriving and supporting drums. They permit extension of the line andchanges in the line loop shape without material change in the drumloadings. As the line or lines, including the buckets, the floats andaccessories, is or are in balance, the

principal load imposed on the driving means is only the inevitablefriction together with the digging and hoisting load of the excavatedmaterial. The amount of float buoyancy can, of course, be changed, sothat as much as desired of the line load can be offset.

In both embodiments of the invention there is provided an underwaterexcavating machine effective under almost all conditions to excavate andremove material from substantial depths without injury to the machineryand with economical and satisfactory operation. The arrangement achievesmultidirectional yielding contact with the bottom material so thatwithin the intended range of use (holding and movement) the forcesdeveloped by the mass of the floating system are not deleteriouslyimposed on any part. Conversely, the forces developed by the bucketsduring excavation are not deleteriously impressed upon the remainder ofthe structure. This assists the arrangement in excavating well under thedesign conditions and at great depths not otherwise possible.

From the foregoing it is seen that the endless succession of flexiblyconnected excavating buckets 64 forms an endless loop that is supportedin a vertical plane from a pair of rotatable supporting means which arewithin the loop at its upper end. The length of the loop suspended belowthe drums tends to hang freely along a catenary curve, as seen in FIGS.A to D inclusive. This succession of buckets is circulated in onedirection providing a descending portion extending downwardly from oneof said supporting means, a bottom portion, the buckets of which are indigging and filling engagement with the bed of material to be excavated,and an ascending portion that extends from the lower portion to theother of said supporting means. Guide means, within the loop at thelower end of the descending portion guides the descending portion alonga predetermined path from said one of said supporting means with theascending portion freely suspended from the other supporting means, itbeing understood that the drum 62, if and when used, is merely asupplemental guide which does not support the loop.

Means above the lower portion supports the guide means for movement todifferent positions within said plane for varying the path of travel ofsaid descending portion, and actuating means is provided for effectingmovement of the guide means to said different positions, and one of thesupporting means is movable toward the other for varying the downwardlength of the suspended portion of the loop and the digging depth of thebuckets along the lower portion, as seen in FIGS. B through D.

The means for flexibly connecting of the buckets of the successionpermit free movement of the buckets of adjacent pairs vertically alongthe lower portion of the loop independently of the guide means when indigging engagement with the material to be excavated, thus preventingstrain or injury to the buckets should the guide means unexpectedly movedownwardly or should the buckets move upwardly on meeting obstacles inthe material.

Where the succession of buckets and its supports and the guide means areon a floating hull, they will remain substantially in a vertical planeupon surging or rolling of the hull under the influence of naturalforces, such as waves, wind, etc. or other forces such as unbalancing ofthe hull.

In operation, the foregoing structure enables performance of the steps,in a method, of suspending in a substantially vertical plane from a pairof generally horizontally spaced points of suspension, an endlesssuccession of excavating buckets in the form of a loop with the pointsof suspension within the upper portion of the loop and with theremainder of the loop below said points tending to hang freely along acatenary curve.

When the succession is circulated in one direction a descending portionof the loop extends from one of said points to the lower portion of theloop, and an ascending portion extends from said lower portion to theother point of suspension, with the buckets at the lower portion indigging engagement with the material of the bed.

The step of increasing the digging depth of the buckets along the lowerportion may be affected by simultaneously increasing the length of theloop suspended below said suspension points and decreasing the length ofthe loop above and extending between the points of suspension. One waythis step, in turn, may be accomplished is by moving one of said pointsof suspension different distances toward the other, as seen in FIGS. Bthrough D.

The apparatus as described also enables the step of yieldably holdingthe descending portion in a path ex tending vertically downwardly at aholding point within the loop spaced below one of the points ofsuspension, and supporting a length of the lower portion adjacent theholding point extending generally horizontally in a clean-up positionduring lowering of said lower portion to different distances.

The apparatus further enables the method step of elevating the remainderof the loop, which is the portion suspended from said suspension points,by moving the holding point inwardly and away from the ascending portionas seen in FIG. C.

The method practiced in underwater excavating is one in which thebuckets and appurtenances in the water are buoyed both decreasing thenormal gravitational strain on the succession and the force required forcirculation of the succession.

I claim:

1. The methodof excavating material from a bed thereof that includes thesteps of:

a. suspending in a substantially vertical plane-from a pair of generallyhorizontally spaced points of suspension, an endless succession ofexcavating buckets in the form of a loop with said points within theupper portion of said loop and with the remainder below said pointstending to hang freely along a catenary curve;

b. moving said succession to circulate the same in onedirection'providing a descending portion of said loop from one of saidpoints to a lower portion at the bottom of said loop and an ascendingportion from said lower portion to the other point of suspension withthe buckets at said lower portion in digging engagement with thematerial of said bed during said movement;

0. progressively lowering said lower portion relative to said points ofsuspension to lower the digging depth of the buckets of said lowerportion different distances downwardly by simultaneously increasing thelength of the loop suspended below said points and decreasing the lengthof the loop above said remainder and extending between said points,during said circulation of the buckets of said succession.

2. In the method as defined in claim 1:

d. the step of simultaneously increasing and decreasing said lengthsbeing effected by moving one of said points of suspension differentdistances from the other.

3. The method as defined in claim 1 that includes the step of:

d. yieldably holding said descending portion of said succession in apath extending generally vertically downwardly from said one of saidsuspension points to said lower portion at a holding point within saidloop spaced below said one of said points and supporting a length ofsaid lower portion adjacent said holding point in a generallyhorizontally extending clean-up position during said lowering of saidlower position to said different distances downwardly.

4. The method as defined in claim 3 that includes the step of:

e. elevating said'remainder of said loop to different distances in saidplane while maintaining said holding point in engagement with said loopby moving said holding point in a direction upwardlyand away from saidascending portion.

5. The method as defined in claim 3:

e. yieldably supporting each of the buckets of said succession formovement independently of the others relative to the'length of saidlower portion under the influence of variations in the resistance ofsaid bed during digging.

6. The method of underwater excavation of material of a bed thereofbelow a body of water that includes the steps of:

a; suspending in a substantially vertical plane from pair of generallyhorizontally spaced points of suspension floatingly supported above saidbody an endless succession of excavating buckets in the form of a loopextending into said'body with said points within the upper portion ofsaid loop and with the remainder below said points tending to hangfreely along a catenary curve;

b. moving said succession to circulate the same in one directionproviding a descending portion of said loop from one of said points to alower portion at the bottom of said loop and an ascending portion fromsaid lower portion to the other point of suspension with the buckets atsaid lower portion in digging engagement with the material of said bedduring said movement;

c. progressively lowering sad lower portion relative to said points ofsuspension to lower the digging depth of the buckets of said lowerportion different distances downwardly by simultaneously increasing thelength of the loop suspended from and below said points and decreasingthe length of the loop extending above said remainder and between saidpoints during said circulation of the buckets of said succession. I

7. The method as defined in claim 6 that includes the step of:

d. holding said descending portion in a path extending generallyvertically downwardly from said one of said points of suspension to saidlower portion at a holding point within said loop at said lower portionspaced below said one of said points of suspension, and supporting alength of said lower portion adjacent said holding point in a generallyhorizontally extending clean-up position extending from the lower end ofsaid descending portion during said lowering of said lower portion ateach of said distances downwardly.

8. The method as defined in claim 7 that includes the step of:

e. pendulously supporting said points of suspension and said loop andholding point in said plane from a hull floating on body of waterwhereby said loop, points of suspension, and holding point, will remainsubstantially stable in said plane relative to movement of said hullfrom wave force and other natural forces.

9. The method as defined in claim 7 that includes the step of:

e. moving said holding point downwardly to said different distancessimultaneously with downward lowering of said lower portion byapplication of progressively increasing downward force to said holdingpoint and yieldably holding said holding point at each of said differentdistances.

10. The method as defined in claim 6 that includes the step of:

d. buoying the succession of buckets submerged within said body againstthe force of gravity thereby decreasing the normal gravitational strainon said succession and the normal force required for circulationthereof.

11. The method as defined in claim 6 that includes the step of:

d. yieldably holding said descending portion in a path extendinggenerally vertically downwardly from one of said points of suspension tosaid lower portion at a holding point within said loop spacedsubstantially vertically below said one of said points of suspension andsupporting a length of said lower portion in a generally horizontallyextending cleanup position extending from the lower end of saiddescending portion at each of said distance downwardly.

12. An excavating machine comprising:,

a. a hull adapted to be floatingly supported on a body of water in aposition spaced above a bed of material to be excavated;

b. an endless row of spaced excavating buckets, each having spaced sidewalls, a leading digging end, and a trailing end, connected for movementlongitudinally of said row with their digging ends facing one direction;7

c. line-means extending longitudinally of saidrow connecting saidbuckets for simultaneous movement in said one direction and drivingmeans on said hull in driving engagement with said line means foreffecting said movement;

d. a pair of horizontally spaced suspending means on said hullsuspending said line connecting means and said row of buckets in a loopof generally catenary shape depending below said support in a verticalplane providing a horizontally extending upper portion at said hull anda descending and as cending portion respectively extending downwardlyfrom the ends of said horizontally extending portion to a lower diggingportion for digging engagement at said lower portion with the materialto be excavated when the buckets of said row are moved in said onedirection;

e. supporting means supporting one of said suspending means on said hullfor horizontal movement toward and away from the other suspending meansfor varying the digging depth of the buckets at said lower portionduring movement of said line-means and buckets in said one direction;

f. means connected with said supporting means for moving the latter andthe suspending means supported thereon toward and away from said otherof said suspending means;

g. guide means carried by said hull supported within said loop inengagement with said line-means at said lower portion and verticallybelow said one of said suspending means for movement vertically todifferent positions relative to said hull for changing the catenaryshape of said row and for varying the excavating depth of said lowerportion with the buckets of said ascending portion freely suspended fromsaid suspending means at each of the different digging depths; and

h. guide moving means operatively connected with said guide means formoving said guide means to said different positions.

13. An excavating machine as defined in claim 12 including:

i. said guide means and said one of said suspending means beingconnected for upward movement of said guide means simultaneously withmovement of said one of said suspending means away from said other ofsaid suspending means, and for downward movement of said guide meanssimultaneously with movement of said one of said suspending means towardthe other, whereby said guide means will be substantially verticallybelow said one of said suspending means during movement of said one ofsaid suspending means toward and away from the other.

14. An excavating machine as defined in claim 12:

i. mounting means for pendulously supporting'said suspending means,supporting means, guide means, bucket line and buckets substantially insaid vertical plane during movement of said hull under the influence ofwaves and other natural forces.

15. In an excavating machine as defined in claim 12:

i. said line means comprising a pair of horizontally spaced, parallel,endless, flexible bucket lines in side-by-side relation extending acrossand in engagement with said suspending means and said guide means, andparallel, adjacent pairs of rigid spacers extending horizontally betweensaid pair of bucket lines and secured at their ends to the latterholding said bucket lines in spaced relation to each other and saidspacers being uniformly spaced apart in a direction longitudinally ofsaid bucket lines, with one excavating bucket for each adjacent pair ofspacers;

j. a first pair of flexible bridle lines of equal length connectingopposite sides of each bucket adjacent its leading end with the bucketlines of said pair thereof adjacent opposite ends of one of saidspacers, and a second pair of flexible bridle lines of equal lengthconnecting the opposite sides of each bucket adjacent its trailing endwith the bucket lines adjacent opposite ends of the spacer adjacent saidone spacer but rearwardly thereof relative to the direction of movementof said bucket lines, said first and second pair of bridle linesextending divergently away from said leading and trailing endsrespectively for holding said buckets against overturning and betweensaid lines.

16. In an excavating machine as defined in claim 15:

k. said first pair of bridle lines being longer than said second pair ofbridle lines and the lengths of the lines of said first pair being lessthan the distance between adjacent spacers, whereby said buckets will besuspended vertically from said ascending portion with their digging endsuppermost during their upward movement with said ascending portion.

17. In an excavating machine as defined in claim 15:

1. said spacers being buoyant to reduce the load of the filled bucketson said bucket lines along said ascending portion of said line-means.

18. In an excavating machine as defined in claim 12:

i. said guide means including a substantially vertically disposed boomadjacent said one of said suspending means having a fairlead at itslower end in said engagement with said lower portion of said line meanswithin said loop; and

j. said guide moving means being connected with said boom for movingsaid boom vertically to carry said fairlead to said different positions.

19. In an excavating machine as defined in claim 18:

k. a boom support for supporting said boom for swinging its lower endincluding said fairlead upwardly and rearwardly in a direction away fromsaid ascending portion of said line-means for elevating said line-meansand buckets above said bed for moving said hull and buckets from onedigging site to another. for

20. In an excavating machine as defined in claim 12:

i. means for yieldably supporting said guide means at each of saiddifferent positions for upward movement under predetermined upward forcethereagainst due to rise and fall of said hull under the influence ofwaves, and swells and other natural forces.

21. An underwater excavator comprising the combination of:

a. a hull adapted to be floatingly supported on a body of water in aposition spaced above material to be excavated;

b. an endless succession of buckets and an endless, flexible line-meansflexibly connecting said buckets in the form of a loop;

c. a pair of horizontally spaced, rotatable, line suspending means onsaid hull within said loop supporting said loop suspended therefrom in avertical plane with thepart below said suspending means suspendedtherefrom in a catenary curve, providing a descending portion extendingfrom one of said suspending means to a lower digging portion and anascending portion extending from said lower portion to the other of saidsuspending means;

d. means for moving said line-means and said endless succession in onedirection for downward movement of said descending portion and upwardmovement of said ascending portion and from said other suspending meansto said one suspending means;

e. a single boom extending from said hull to said lower digging portionand guide means on the means supporting one of said suspending means formovement thereof horizontally on said hull toward and away from saidother suspending means and means for moving said boom for upwardmovement of said guide means upon movement of said one suspending meansaway from said other suspending means, and for downward movement uponmovement of said one suspending means toward said other suspending meansfor varying the digging depth of said lower portion at said guide means,all while moving said endless succession in said one direction.

22. In an excavator as defined in claim 21: g. means flexibly connectingthe buckets of said succession with said line means for movement of saidbuckets along a path spaced below said guide means and for free movementtoward said guide means during movement past the latter to premit saidbuckets to move over irregularities in the surface of said materialwithout engaging said guide means.

1. The method of excavating material from a bed thereof that includesthe steps of: a. suspending in a substantially vertical plane from apair of generally horizontally spaced points of suspension, an endlesssuccession of excavating buckets in the form of a loop with said pointswithin the upper portion of said loop and with the remainder below saidpoints tending to hang freely along a catenary curve; b. moving saidsuccession to circulate the same in one direction providing a descendingportion of said loop from one of said points to a lower portion at thebottom of said loop and an ascending portion from said lower portion tothe other point of suspension with the buckets at said lower portion indigging engagement with the material of said bed during said movement;c. progressively lowering said lower portion relative to said points ofsuspension to lower the digging depth of the buckets of said lowerportion different distances downwardly by simultaneously increasing thelength of the loop suspended below said points and decreasing the lengthof the loop above said remainder and extending between said points,during said circulation of the buckets of said succession.
 2. In themethod as defined in claim 1: d. the step of simultaneously increasingand decreasing said lengths being effected by moving one of said pointsof suspension different distances from the other.
 3. The method asdefined in claim 1 that includes the step of: d. yieldably holding saiddescending portion of said succession in a path extending generallyvertically downwardly from said one of said suspension points to saidlower portion at a holding point within said loop spaced below said oneof said points and supporting a length of said lower portion adjacentsaid holding point in a generally horizontally extending clean-upposition during said lowering of said lower position to said differentdistances downwardly.
 4. The method as defined in claim 3 that includesthe step of: e. elevating said remainder of said loop to differentdistances in said plane while maintaining said holding point inengagement with said loop by moving said holding point in a directionupwardly and away from said ascending portion.
 5. The method as definedin claim 3: e. yieldably supporting each of the buckets of saidsuccession for movement independently of the others relative to thelength of said lower portion under the influence of variations in theresistance of said bed during digging.
 6. The method of underwaterexcavation of material of a bed thereof below a body of water thatincludes the steps of: a. suspending in a substantially vertical planefrom a pair of generally horizontally spaced points of suspensionfloatingly supported above said body an endless succession of excavatingbuckets in the form of a loop extending into said body with said pointswithin the upper portion of said loop and with the remainder below saidpoints tending to hang freely along a catenary curve; b. moving saidsuccession to circulate the same in one direction providing a descendingportion of said loop from one of said points to a lower portion at thebottom of said loop and an ascending portion from said lower portion tothe other point of suspension with the buckets at said lower portion indigging engagement with the material of said bed during said movement;c. progressively lowering said lower portion relative to said points ofsuspension to lower the digging depth of the buckets of said lowerportion different distances downwardly by simultaneously increasing thelength of the loop suspended from and below said points and decreasingthe length of the loop extending above said remainder and between saidpoints during said circulation of the buckets of said succession.
 7. Themethod as defined in claim 6 that includes the step of: d. holding saiddescending portion in a path extending generally vertically downwardlyfrom said one of said points of suspension to said lower portion at aholding point within said loop at said lower portion spaced below saidone of said points of suspension, and supporting a length of said lowerportion adjacent said holding point in a generally horizontallyextending clean-up position extending from the lower end of saiddescending portion during said lowering of said lower portion at each ofsaid distances downwardly.
 8. The method as defined in claim 7 thatincludes the step of: e. pendulously supporting said points ofsuspension and said loop and holding point in said plane from a hullfloating on body of water whereby said loop, points of suspension, andholding point, will remain substantially stable in said plane relativeto movement of said hull from wave force and other natural forces. 9.The method as defined in claim 7 that includes the step of: e. movingsaid holding point downwardly to said different distances simultaneouslywith downward lowering of said lower portion by application ofprogressively increasing downward force to said holding point andyieldably holding said holding point at each of said differentdistances.
 10. The method as defined in claim 6 that includes the stepof: d. buoying the succession of buckets submerged within said bodyagainst the force of gravity thereby decreasing the normal gravitationalstrain on said succession and the normal force required for circulationthereof.
 11. The method as defined in claim 6 that includes the step of:d. yieldably holding said descending portion in a path extendinggenerally vertically downwardly from one of said points of suspension tosaid lower portion at a holding point within said loop spacedsubstantially vertically below said one of said points of suspension andsupporting a length of said lower portion in a generally horizontallyextending clean-up position extending from the lower end of saiddescending portion at each of said distances downwardly.
 12. Anexcavating machine comprisiNg: a. a hull adapted to be floatinglysupported on a body of water in a position spaced above a bed ofmaterial to be excavated; b. an endless row of spaced excavatingbuckets, each having spaced side walls, a leading digging end, and atrailing end, connected for movement longitudinally of said row withtheir digging ends facing one direction; c. line-means extendinglongitudinally of said row connecting said buckets for simultaneousmovement in said one direction and driving means on said hull in drivingengagement with said line means for effecting said movement; d. a pairof horizontally spaced suspending means on said hull suspending saidline connecting means and said row of buckets in a loop of generallycatenary shape depending below said support in a vertical planeproviding a horizontally extending upper portion at said hull and adescending and ascending portion respectively extending downwardly fromthe ends of said horizontally extending portion to a lower diggingportion for digging engagement at said lower portion with the materialto be excavated when the buckets of said row are moved in said onedirection; e. supporting means supporting one of said suspending meanson said hull for horizontal movement toward and away from the othersuspending means for varying the digging depth of the buckets at saidlower portion during movement of said line-means and buckets in said onedirection; f. means connected with said supporting means for moving thelatter and the suspending means supported thereon toward and away fromsaid other of said suspending means; g. guide means carried by said hullsupported within said loop in engagement with said line-means at saidlower portion and vertically below said one of said suspending means formovement vertically to different positions relative to said hull forchanging the catenary shape of said row and for varying the excavatingdepth of said lower portion with the buckets of said ascending portionfreely suspended from said suspending means at each of the differentdigging depths; and h. guide moving means operatively connected withsaid guide means for moving said guide means to said differentpositions.
 13. An excavating machine as defined in claim 12 including:i. said guide means and said one of said suspending means beingconnected for upward movement of said guide means simultaneously withmovement of said one of said suspending means away from said other ofsaid suspending means, and for downward movement of said guide meanssimultaneously with movement of said one of said suspending means towardthe other, whereby said guide means will be substantially verticallybelow said one of said suspending means during movement of said one ofsaid suspending means toward and away from the other.
 14. An excavatingmachine as defined in claim 12: i. mounting means for pendulouslysupporting said suspending means, supporting means, guide means, bucketline and buckets substantially in said vertical plane during movement ofsaid hull under the influence of waves and other natural forces.
 15. Inan excavating machine as defined in claim 12: i. said line meanscomprising a pair of horizontally spaced, parallel, endless, flexiblebucket lines in side-by-side relation extending across and in engagementwith said suspending means and said guide means, and parallel, adjacentpairs of rigid spacers extending horizontally between said pair ofbucket lines and secured at their ends to the latter holding said bucketlines in spaced relation to each other and said spacers being uniformlyspaced apart in a direction longitudinally of said bucket lines, withone excavating bucket for each adjacent pair of spacers; j. a first pairof flexible bridle lines of equal length connecting opposite sides ofeach bucket adjacent its leading end with the bucket lines of said pairthereof adjacent opposite ends of one of said spacers, and a second pairof flexible bridle lines of equal Length connecting the opposite sidesof each bucket adjacent its trailing end with the bucket lines adjacentopposite ends of the spacer adjacent said one spacer but rearwardlythereof relative to the direction of movement of said bucket lines, saidfirst and second pair of bridle lines extending divergently away fromsaid leading and trailing ends respectively for holding said bucketsagainst overturning and between said lines.
 16. In an excavating machineas defined in claim 15: k. said first pair of bridle lines being longerthan said second pair of bridle lines and the lengths of the lines ofsaid first pair being less than the distance between adjacent spacers,whereby said buckets will be suspended vertically from said ascendingportion with their digging ends uppermost during their upward movementwith said ascending portion.
 17. In an excavating machine as defined inclaim 15: l. said spacers being buoyant to reduce the load of the filledbuckets on said bucket lines along said ascending portion of saidline-means.
 18. In an excavating machine as defined in claim 12: i. saidguide means including a substantially vertically disposed boom adjacentsaid one of said suspending means having a fairlead at its lower end insaid engagement with said lower portion of said line means within saidloop; and j. said guide moving means being connected with said boom formoving said boom vertically to carry said fairlead to said differentpositions.
 19. In an excavating machine as defined in claim 18: k. aboom support for supporting said boom for swinging its lower endincluding said fairlead upwardly and rearwardly in a direction away fromsaid ascending portion of said line-means for elevating said line-meansand buckets above said bed for moving said hull and buckets from onedigging site to another. for
 20. In an excavating machine as defined inclaim 12: i. means for yieldably supporting said guide means at each ofsaid different positions for upward movement under predetermined upwardforce thereagainst due to rise and fall of said hull under the influenceof waves, and swells and other natural forces.
 21. An underwaterexcavator comprising the combination of: a. a hull adapted to befloatingly supported on a body of water in a position spaced abovematerial to be excavated; b. an endless succession of buckets and anendless, flexible line-means flexibly connecting said buckets in theform of a loop; c. a pair of horizontally spaced, rotatable, linesuspending means on said hull within said loop supporting said loopsuspended therefrom in a vertical plane with the part below saidsuspending means suspended therefrom in a catenary curve, providing adescending portion extending from one of said suspending means to alower digging portion and an ascending portion extending from said lowerportion to the other of said suspending means; d. means for moving saidline-means and said endless succession in one direction for downwardmovement of said descending portion and upward movement of saidascending portion and from said other suspending means to said onesuspending means; e. a single boom extending from said hull to saidlower digging portion and guide means on the lower end of said boomsupported within said loop at said lower portion vertically below saidone suspending means for positioning buckets of the loop at said lowerportion substantially directly below said one suspending means indigging relation to said material, and for holding said descendingportion freely hanging from said one suspending means to said guidemeans with said ascending portion hanging freely in a catenary curvefrom said other suspending means toward said guide means; f. meanssupporting one of said suspending means for movement thereofhorizontally on said hull toward and away from said other suspendingmeans and means for moving said boom for upward movement of said guidemeans upon movement of said one suspending means awaY from said othersuspending means, and for downward movement upon movement of said onesuspending means toward said other suspending means for varying thedigging depth of said lower portion at said guide means, all whilemoving said endless succession in said one direction.
 22. In anexcavator as defined in claim 21: g. means flexibly connecting thebuckets of said succession with said line means for movement of saidbuckets along a path spaced below said guide means and for free movementtoward said guide means during movement past the latter to premit saidbuckets to move over irregularities in the surface of said materialwithout engaging said guide means.